The present invention relates generally to a semiconductor devices, and more particularly to a self-aligned bipolar transistor (BJT).
A bipolar transistor, sometimes simply referred to as a bipolar transistor or a BJT, is a circuit element in an integrated circuits due to its high speed switching capability and current carrying capacity. A bipolar transistor uses holes and electrons to conduct electrical current.
The bipolar transistor has an emitter, a collector, and a base interposed between the emitter and the collector. Typically, the emitter and collector are of one conductivity type of semiconductor, while the base is of an opposite type, thereby forming two pn junctions. Modulating the current injected into the base terminal of a bipolar transistor will modulate the current flowing through the pn junctions of the base from the emitter to the collector.
BJT fabrication methods have attempted to reduce BJT dimensions and increase the ease and reliability of manufacture. Directional deposition and layer undercutting are two of the many techniques employed in the existing art, to reduce BJT dimensions and self-align HBT structures. Such techniques, however, tend to be process-sensitive and difficult to control, so that the yield, reliability, performance, and production costs associated with devices thus fabricated also are difficult to control.